package leetcode.greedy;

public class prefixTree {
    public static class TrieNode{
        public int pass;
        public int end;
        public TrieNode[] nexts;

        public TrieNode(){
            pass =0;
            end = 0;
            nexts = new TrieNode[26];
        }
    }
    public static class Trie{
        private TrieNode root;
        public Trie(){
            root = new TrieNode();
        }
        public void insert(String word){//插入一个字符
            if (word == null) return;
            char[] chs = word.toCharArray();
            TrieNode node = root;
            node.pass++;
            int index = 0;
            for (int i = 0; i < word.length() ; i++) {
                index = chs[i] - 'a';
                if (node.nexts[index] == null)
                    node.nexts[index] = new TrieNode();
                    node = node.nexts[index];
                    node.pass++;
            }
            node.end++;
        }

        public int search(String word){//寻找该字符插入了几个

            if (word == null) return 0;

            char[] chars = word.toCharArray();

            TrieNode node = root;

            int index = 0;

            for (int i = 0; i < chars.length ; i++) {

                index = chars[i] - 'a';

                if (node.nexts[index] == null) return 0;

                node = node.nexts[index];
            }
            return node.end;
        }

        public int prefixNumber(String pre){//寻找前缀数量

            if (pre == null) return 0;

            char[] chars = pre.toCharArray();

            TrieNode node = root;

            int index = 0;

            for (int i = 0; i < chars.length; i++) {

                index = chars[i] - 'a';

                if(node.nexts[index] == null) return 0;

                node = node.nexts[index];
            }
            return node.pass;
        }

        public void delete(String word){

            if (search(word) != 0){
                char[] chars = word.toCharArray();
                TrieNode node = root;
                node.pass--;
                int index = 0;
                for (int i = 0; i < chars.length; i++) {
                    index = chars[i] - 'a';

                    if (node.nexts[index].pass == 0){
                        node.nexts[index] = null;
                        return;
                    }
                    node = node.nexts[index];
                }
                node.end--;
            }
        }
    }
}
